JP2008230219A - Solution casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a film with a high quality having no optical unevenness by suppressing an increasing in an organic matter adhered to the surface of a substrate. <P>SOLUTION: A casting film 33 is formed by casting a dope 21 on a casting drum 32 the surface of which is made to be cooled. The casting film 33 is peeled and before the dope is casted, cleaning gas containing dry ice particles is brown to the surface of the casting drum 32 with a drum cleaning unit 41. The dry ice particles collide to the surface of the casting drum 32, and the colliding energy is effective of removing from the surface an organic matter adhered on the casting drum 32. The organic matter mainly contains aliphatic acid aliphatic acid ester, metal salt of aliphatic acid. Befor the increase of the amount of the organic matter, it is removed and therefore isn't transmitted onto the surface of the casting film. Thus a film 20 with a high quality having no optical unevenness is produced without lowering the productivity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solution casting method suitable for manufacturing an optical film such as a protective film for a polarizing plate of a liquid crystal display device, an optical compensation film, and a viewing angle widening film.

  Conventionally, a polymer film (hereinafter referred to as a film) has been used as a photographic photosensitive film or the like because it is excellent in light transmittance and flexibility, is lightweight, and can be reduced in size and thickness. Recently, a cellulose acylate film made from cellulose acylate is used to protect the surface of the polarizing plate of a liquid crystal display device because of its excellent toughness and low birefringence in addition to the above features. The film is used as various optical films such as a protective film, an optical compensation film, and a viewing angle widening film, and the demand for the liquid crystal display device is remarkably increased.

  The optical film is generally made by a solution casting method. The solution casting method is that a cast film is formed by casting a dope containing a polymer such as cellulose acylate, a solvent, and an additive on a traveled support, and then casting from the support. Is a film forming method in which the film is peeled off and dried to form a film. In addition to being able to form a film without causing thermal damage, the solution film-forming method is excellent in light transmittance, optical isotropy, and thickness uniformity by devising a film forming process, and contains less foreign matter. It has characteristics such as being able to obtain a film.

  By the way, when the film is continuously formed by the solution casting method, the surface of the support is soiled. This stain is considered to be caused by the deposition of organic substances mainly composed of fatty acids, fatty acid esters, fatty acid metal salts and the like contained in the cast film on the surface of the support. The organic matter becomes larger as time passes from the start of film formation, and the smoothness of the support surface is impaired. The increased organic matter is transferred to the surface of the casting film and causes optical unevenness of the film. Further, when the organic matter increases, the organic material cannot be smoothly peeled off, and in the worst case, peeling becomes impossible and the film formation needs to be temporarily interrupted. If organic matter adheres in this way, various problems such as a decrease in productivity occur. Therefore, at the film forming site, the surface of the support is regularly washed with a nonwoven fabric or the like. However, in this method, it is necessary to reduce the film formation speed or to stop the film formation once, so that a reduction in productivity is regarded as a problem.

Therefore, as a method for cleaning the surface of the support without reducing productivity, for example, Patent Document 1 discloses that the surface of the support is irradiated by irradiating light on the surface of the support and measuring the reflectance. There has been proposed a method of confirming the adhering organic matter and wiping the surface of the support continuously or intermittently with a nonwoven fabric or the like soaked with a solvent according to the state of occurrence.
JP 2003-001654 A

  However, in Patent Document 1, since the surface of the support is washed after the presence of the organic substance is confirmed, an increase in the organic substance cannot be suppressed, and the quality of the completed film cannot be avoided. In addition, if the surface of the support is cleaned with a solvent, traces of the solvent are likely to remain on the surface of the support, so that streaky irregularities and irregularities due to the traces of the solvent are formed on the surface of the cast film. There is a possibility that the flatness is lowered. In addition, if the surface of the support is wiped with a non-woven fabric or the like, hard foreign matter may be mixed between the non-woven fabric and the support and the surface of the support may be damaged. If the dope is cast on a damaged support, scratches appear on the surface of the cast film, which causes optical unevenness of the film.

  Therefore, the present invention aims to solve the above-mentioned problems, and manufactures a high-quality film without inducing optical unevenness by suppressing an increase in organic matter adhering to the support without reducing productivity. An object of the present invention is to provide a solution casting method.

  In order to achieve the above object, the solution casting method of the present invention comprises a step of casting a dope containing a polymer and a solvent on the surface of a support that runs endlessly to form a cast film, Peeling the cast film and drying it to form a film; washing the surface of the support until the dope is cast after the cast film is peeled off; And a cleaning process that suppresses an increase in the amount of attached organic matter. In the cleaning step, it is preferable that a cleaning gas containing granular dry ice is sprayed on the surface of the support body constantly or intermittently by a cleaning gas spraying means.

  In the cleaning step, a dry ice supply unit that supplies the dry ice, a carrier gas supply unit that supplies a carrier gas that transports the dry ice to the surface of the support, and the dry ice is mixed with the carrier gas. The first piping connecting the dry ice supply unit and the cleaning gas generating unit by spraying the cleaning gas onto the surface of the support by the cleaning gas spraying means having the cleaning gas generating unit for generating the cleaning gas The carrier gas is measured by a second flow rate measuring unit provided in a second pipe that connects the carrier gas supply unit and the cleaning gas generating unit while measuring the flow rate of the dry ice by a first flow rate measuring unit provided in Based on the flow rate of the dry ice and the flow rate of the carrier gas measured by the first and second flow rate measuring units. Te, it is preferable that feedback control of the supply amount of the supply amount and the carrier gas of the dry ice.

  In the cleaning step, the pressure in the first pipe is measured by a pressure measuring unit provided in the first pipe, and the dry ice is measured based on the pressure in the first pipe measured by the pressure measuring unit. It is preferable to feedback control the supply pressure. In the cleaning step, the temperature of the dry ice is measured by a temperature measuring unit provided in the first pipe, and the temperature of the dry ice is feedback-controlled based on the temperature of the dry ice measured by the temperature measuring unit. It is preferable to do.

  In the cleaning step, the gloss of the surface of the support is measured by a gloss measuring unit provided on the downstream side of the support in the running direction with respect to the cleaning gas spraying means, and the surface of the support is predetermined. The cleaning time required to make the glossiness of the above is measured by a time measurement unit, based on the glossiness of the surface of the support measured by the glossiness measurement unit and the cleaning time measured by the time measurement unit, It is preferable to control the amount of cleaning gas sprayed.

  In the washing step, it is preferable to irradiate the surface of the support with ultraviolet rays constantly or intermittently. In the cleaning step, it is preferable to irradiate the surface of the support with plasma constantly or intermittently. In the cleaning step, it is preferable to irradiate the surface of the support with a laser constantly or intermittently. It is preferable that the surface of the support is cooled to −10 ° C. or more and 10 ° C. or less, and the cast film is gelled to have self-supporting property. Preferably, the polymer is cellulose triacetate, and the organic substance includes any one of fatty acid, fatty acid ester, and fatty acid metal salt.

  In the present invention, without increasing the film forming speed, the surface of the support is washed until the dope is cast after the cast film is peeled off, thereby suppressing the increase of organic substances adhering to the support. To do. This makes it possible to produce a high-quality film without optical unevenness without reducing productivity. Further, by using a predetermined cleaning method, the cleaning operation can be performed without damaging the surface of the support.

  Hereinafter, the present invention will be specifically described with reference to embodiments according to the present invention. However, the forms listed here are merely examples according to the present invention, and do not limit the present invention.

[Solution casting method]
As shown in FIG. 1, the film manufacturing equipment 10 used in this embodiment includes a stock tank 11, a casting chamber 12, a transition portion 13, a tenter 14, a drying chamber 15, a cooling chamber 16, a winding chamber. And chamber 17.

  The stock tank 11 is for storing the dope 21 that is a raw material of the film 20, and includes a stirring blade 11 b that is rotated by a motor 11 a and a jacket 11 c for adjusting the internal temperature of the stock tank 11. Yes. The jacket 11c is provided on the outer peripheral surface of the stock tank 11, and a heat transfer medium whose temperature is adjusted is supplied into the jacket 11c. Thereby, the internal temperature of the stock tank 11 is controlled within a predetermined range, and the temperature of the dope 21 stored in the stock tank 11 is kept substantially constant. The stirring blade 11b is rotated by the motor 11a and the dope 21 is constantly stirred. Thereby, uniform quality is maintained without generating aggregates or the like in the stored dope 21. Further, a pump 25 and a filtering device 26 are provided downstream of the stock tank 11. The dope 21 will be described later in detail.

  The casting chamber 12 includes a casting die 30 for casting the dope 21, a casting drum 32 acting as a support, a decompression chamber 34 for decompressing the vicinity of the discharge port of the casting die 30, and the casting chamber 12. A temperature control equipment 35 for adjusting the internal temperature of the film, a stripping roller 36 used when stripping the casting film 33 from the casting drum 32, a heat transfer medium circulating device 37 connected to the casting drum 32, A condenser (condenser) 39, a recovery device 40, and a drum washer 41 are installed.

  The casting die 30 is formed with a discharge port for the dope 21, and the discharge port is installed in a state of opening toward the casting drum 32. The material of the casting die 30 is preferably a material having characteristics such as high corrosion resistance to an electrolyte aqueous solution, a mixed solution of dichloromethane, methanol, etc., and a low coefficient of thermal expansion. Further, the finishing accuracy of the wetted surface of the casting die 30 is preferably a surface roughness of 1 μm or less, and the straightness is preferably 1 μm / m or less in any direction. If such a casting die 30 is used, the casting film 33 without streaks and unevenness can be formed on the casting drum 32.

  The casting drum 32 is rotated around a cylindrical axis by a driving device. The casting drum 32 has a cylindrical shape or a columnar shape, and the surface thereof is subjected to chrome plating for the purpose of providing sufficient corrosion resistance and strength. A flow path for a heat transfer medium is formed inside the casting drum 32. This heat transfer medium is supplied from a heat transfer medium circulation device 37 attached to the casting drum 32. By passing or circulating the heat transfer medium through the flow path, the surface temperature of the casting drum 32 is maintained at a desired temperature. In addition, as a support body that replaces the casting drum 32, a casting band that runs around an endlessly on a rotating roller can be suitably used.

  The decompression chamber 34 is installed on the casting roller 30 side of the casting die 30, and the back side of the dope 21 flow (casting bead) formed between the casting die 30 and the casting drum 32 is desired. Reduce the pressure to The back side of the casting bead is a surface that comes into contact with the surface of the casting drum 32 later. The stripping roller 36 supports the casting film 33 that is stripped from the casting drum 32. The condenser 39 condenses and liquefies the gas containing the solvent evaporated from the inside of the dope 21 and the casting film 33, and the recovery device 40 is for recovering the condensed and liquefied organic solvent. The recovered solvent is regenerated as a solvent for dope preparation after being regenerated by the regenerator.

  The drum cleaner 41 is installed in the vicinity of the surface of the casting drum 32 and after the casting film 33 is peeled off, until the dope 21 is cast on the casting drum 32 again. . The drum cleaner 41 removes organic substances by spraying a predetermined cleaning gas on the surface of the casting drum 32. Examples of the organic substance include those mainly composed of fatty acid esters, fatty acids, and fatty acid metal salts. However, the organic matter to be removed is not limited to fatty acids and the like, and may be generated, for example, between a fatty acid contained in a polymer used as a raw material for a film and an alcohol contained in a solvent. In addition, it may be generated between the additive added when preparing the dope and the alcohol contained in the solvent. In addition, after collecting the organic substance present on the surface of the casting drum 32 as a sample, the organic component is IR (infrared spectrophotometer), GCMS (gas chromatograph mass spectrometer), NMR (nuclear magnetic resonance apparatus). ) Etc. to confirm.

  The cleaning gas is preferably one in which granular dry ice is included in air, but a gas such as nitrogen or an inert gas may be used instead of air. An air supply device 68 for supplying air is connected to the drum cleaning machine 41 through a pipe 68a. The air supply device 68 is provided with a timer for controlling the air supply time and a pressure regulator, and supplies air by adjusting the pressure to the pipe 68a for the time set by the timer. . Examples of the pressure regulator include those having a cylinder filled with air and a temperature controller for adjusting the temperature of the air in the cylinder. A pipe 69a connected to a dry ice supply device 69 is connected to the pipe 68a. The dry ice supply device 69 is provided with a timer and a flow rate controller for controlling the size and ratio of the dry ice particles, and the dry ice particles whose particle size is adjusted for a predetermined time and minutes are connected to the pipe 69a. To supply.

  A large number of rollers and an air blower 13a are installed in the crossing portion 13 disposed downstream of the casting chamber 12. The tenter 14 is a drying device provided with a plurality of pins as means for holding both side ends of the wet film 38, and the drying of the wet film 38 proceeds to form the film 20.

  The edge-cutting device 43 installed downstream of the tenter 14 cuts both end portions of the film 20. A crusher 44 is attached to the ear clip device 43, and the cut piece of the film 20 is crushed into chips.

  The drying chamber 15 is provided with a large number of rollers 47 and a solvent adsorption / recovery device 48, where the film 20 is sufficiently dried. The cooling chamber 16 provided in the drying chamber 15 cools the film 20 heated in the drying chamber 15 to substantially room temperature. A forced static elimination device (static elimination bar) 49 for adjusting the charged voltage of the film 20 is provided downstream of the cooling chamber 16. In the present embodiment, a knurling application roller 50 for applying knurling to the film 20 is provided on the downstream side of the forced static elimination device 49. Inside the winding chamber 17, a winding roller 51 for winding the film 20 and a press roller 52 for pressing the film 20 are provided.

  Next, an example of a method for manufacturing the film 20 by the film manufacturing facility 10 will be described. In the stock tank 11, a heat transfer medium is caused to flow inside the jacket 11c, and the temperature of the dope 21 is adjusted to 25 to 35 ° C. Moreover, the stirring blade 11b is always rotated, and the quality of the dope 21 is kept uniform. An appropriate amount of the dope 21 is appropriately sent from the stock tank 11 to the filtration device 26 equipped with a filter by the pump 25, and impurities in the dope 21 are removed.

  The casting drum 32 is continuously rotated at a predetermined rotational speed by a driving device. Further, the heat transfer medium is supplied from the heat transfer medium circulation device 37 to the flow path inside the casting drum 32, and the surface temperature thereof is kept substantially constant in the range of −10 to 10 ° C. The dope 21 is cast on the casting drum 32 from the discharge port of the casting die 30. The temperature of the dope 21 used for casting is preferably 30 to 35 ° C. The dope 21 that has reached the surface of the casting drum 32 is quickly cooled, and a gel-like casting film 33 is formed in a short time. As the casting film 33 stays on the casting drum 32 for a longer time, the cooling proceeds and the gelation of the casting film 33 is further promoted. If the casting drum 32 having the surface cooled in this way is used as a support, the casting film 33 having self-supporting properties can be formed in a short time, and therefore the production speed can be improved. . The casting film 33 having the self-supporting property is peeled off from the casting drum 32 while being supported by the peeling roller 36 to form a wet film 38.

  The internal temperature of the casting chamber 12 is adjusted by the temperature control equipment 35 so as to be substantially constant in the range of 10 to 30 ° C. In this embodiment, the solvent gas evaporated from the dope 21 and the casting film 33 existing in the casting chamber 12 is condensed and liquefied by the condenser 39, and then recovered by the recovery device 40 and further regenerated by the regeneration device. And reused as a solvent for dope preparation.

  The wet film 38 sent to the transfer section 13 is in a state containing a large amount of solvent. In the transfer part 13, while supporting the wet film 38 with each roller and conveying it, drying air is supplied from the air blower 13a and the drying of the wet film 38 is advanced.

  In the tenter 14, a large number of pins are inserted into both end portions of the wet film 38 in the vicinity of the entrance, and both end portions of the wet film 38 are held. While the wet film 38 is transported through the inside of the tenter 14 while the both side edges are held, the drying proceeds and becomes the film 20. In the vicinity of the exit of the tenter 14, the pins are pulled out from both ends of the film 20 to release the holding.

  A clip tenter may be provided downstream of the tenter 14 to dry the film 20. The clip tenter is a drying device provided with a plurality of clips as gripping means for gripping both side ends of the film 20. Each clip is attached to a chain that travels endlessly, and moves in the clip tenter according to the movement of the chain. In the clip tenter, after the both ends of the film 20 are gripped by a large number of clips, drying is further promoted while the inside of the film 20 is conveyed. The distance between the clips facing each other when the film 20 is conveyed is widened to apply tension in the width direction of the film 20. A desired retardation value can be imparted by stretching the film 20 in the width direction and adjusting its molecular orientation. The amount of residual solvent in the film 20 immediately before being sent to the clip tenter is preferably 50 to 150% by weight. The residual solvent amount of the present invention indicates the amount of solvent remaining in the film on a dry basis. The amount of residual solvent is calculated by {(xy) / y} × 100, where a sample is taken from the target film, the weight of this sample is x, and the weight of the sample after drying is y. .

  The film 20 is sent to the ear-cutting device 43, and both end portions thereof are cut. The film 20 whose both ends are cut is taken up by the take-up roller 51 in the take-up chamber 17 via the drying chamber 15 and the cooling chamber 16. Both end portions cut by the ear-cutting device 43 are made fine by a crusher 44 and reused as a dope preparation chip.

  As shown in FIG. 2, the drum cleaning machine 41 includes a nozzle 65 attached to the tip of the pipe 68 a and a suction cover 67 provided around the nozzle 65. The suction cover 67 is attached with a suction pipe 67 a connected to a suction device (not shown), and sucks air in the vicinity of the nozzle 65. The drum cleaner 41 is connected to a shift unit (not shown). For the purpose of efficiently blowing the cleaning gas to the surface of the casting drum 32 by the operation of the shift portion, the distance L1 from the blower port 65a formed at the tip of the nozzle 65 to the casting drum 32, or the casting drum 32 The angle θ1 for spraying the cleaning gas is appropriately adjusted.

  The cleaning gas sent to the nozzle 65 via the pipe 68a is blown from the blower port 65a. The dry ice particles in the cleaning gas collide with the surface of the casting drum 32 and the organic matter adhering to the surface of the casting drum 32 is crushed. Since the surface of the casting drum 32 of the present embodiment is cooled in a predetermined temperature range, the dry ice does not sublimate and collides with the casting drum 32. Further, the dry ice particles colliding with the surface of the casting drum 32 are melted by the energy at the time of collision to generate liquid carbon dioxide. This liquid carbon dioxide evaporates while containing the organic matter after dissolving the organic matter. While the organic matter is pulverized and removed, the air around the cleaning portion is sucked by the suction cover 67. Thereby, the pulverized and scattered organic matter can be collected by suction, and problems such as adhesion of the crushed organic matter to the surface of the casting film 33 can be prevented. Note that the suction force is not particularly limited as long as it is appropriately adjusted within a range smaller than the spraying pressure of the cleaning gas.

  The cleaning gas is sprayed on the surface of the casting drum 32 until the dope is cast after the casting film 33 is peeled off. By spraying a gas on the organic matter that has just deposited, it can be efficiently and effectively pulverized and removed before the organic matter increases. In the case of intermittent spraying, it is preferable to perform at least once after the casting film 33 is peeled off and before the dope is cast. However, the number of times is not particularly limited and may be appropriately determined. Further, the cleaning gas is sprayed constantly or intermittently. Which spraying method is used may be determined according to the expected amount of organic matter adhering to the surface of the casting drum 32. The amount of organic matter deposited can be predicted based on the composition of the dope, the surface temperature of the casting drum 32, and the like. For example, when casting a dope that is expected to increase the amount of organic matter deposited, it is effective to always blow the gas, while using a dope that is expected to have a relatively small amount of organic matter precipitated. In some cases, it may be performed intermittently. Thereby, it is possible to maintain a good balance between productivity and energy cost required for spraying.

  The effect of pulverizing the organic matter can be improved by suitably adjusting the distance L1 between the surface of the casting drum 32 and the air outlet 65a, the pressure for blowing the cleaning gas, the average particle size of the dry ice, and the like. The distance L1 between the air outlet 65a and the surface of the casting drum 32 is preferably 0.1 mm or more and 15.0 mm or less, more preferably 0.1 mm or more and 10.0 mm or less, and particularly preferably 0.1 mm. It is 2.0 mm or less. The distance L1 is equal to the length until the cleaning gas sent from the blower port 65a collides with the surface of the casting drum 32. As the distance L1 is longer than 15.0 mm, there is a concern that dry ice particles sublimate before reaching the surface of the casting drum 32, and the energy at the time of collision necessary for pulverizing the organic matter is secured. It is difficult. On the other hand, if L1 is less than 0.1 mm, the energy at the time of the collision becomes too large, so that it is difficult to spray at all times and installation of the apparatus is difficult. Note that L1 is effective for the removal of organic substances if the above range is satisfied, and may be appropriately determined based on ease of installation.

  The pressure for spraying the cleaning gas is preferably 600 kPa to 4000 kPa, more preferably 1000 kPa to 2500 kPa. When the spraying pressure exceeds 4000 kPa, there is a possibility that dry ice particles may be clogged in the nozzle 65 and the surface of the casting drum 32 may be damaged. On the other hand, if it is less than 600 kPa, the energy generated when the cleaning gas collides is small, so that the effect of pulverizing the organic substance is weak. The average particle size of the dry ice particles is preferably 5 μm or more and 20 μm or less. If the particle diameter exceeds 20 μm, the dry ice particles may be too large and damage the surface of the casting drum 32. On the other hand, if the particle size is less than 5 μm, the efficiency of crushing and removing organic substances is reduced. The particle size of the dry ice particles is preferably selected as appropriate according to the size of the organic matter.

In addition to this, in order to further improve the pulverization effect of the organic matter, it is effective to suitably control the cleaning gas spraying time, the angle θ1 formed by the cleaning gas spraying direction and the surface of the casting drum 32. The time for spraying the cleaning gas is preferably 1 × 10 ⁻³ seconds to 5 seconds. More preferably, it is 1 × 10 ⁻² or more and 5 seconds or less. If the cleaning gas spray time exceeds 5 seconds, the surface of the casting drum 32 may be damaged. On the other hand, it is difficult to pulverize organic matter in a short time of less than 1 × 10 ⁻³ seconds. The angle θ1 formed by the direction in which the cleaning gas is blown and the surface of the casting drum 32 is preferably 45 ° or more and 135 ° or less, more preferably 70 ° or more and 110 ° or less, and most preferably 85 ° or more and 95 °. It is as follows. Said angle (theta) 1 is suitably adjusted according to the shape etc. of organic substance. The method of spraying dry ice particles can be applied as a means for cleaning the surface of the casting drum 32 under explosion-proof management.

  The drum washing machine 41 may use one machine or a plurality of machines and is not particularly limited. When using a plurality of drum cleaners 41, they may be juxtaposed in the width direction of the casting drum 32, or a place where organic substances are expected to adhere is specified in advance by casting the dope on a small scale. In addition, it may be randomly installed in the vicinity of the location. In the case of a single machine, the effect of crushing organic substances over a wide range can be obtained by using a scanning type washing machine.

  The apparatus for supplying the cleaning gas in which the dry ice particles as described above are mixed with air is not particularly limited. For example, the cleaning gas may be obtained by using dry ice particles generated by spraying liquid carbon dioxide. Next, with reference to FIG. 3, an embodiment of a drum washer when liquid carbon dioxide is used will be described. As shown in FIG. 3, the drum cleaner 150 includes a first nozzle 151 and a second nozzle 152. Further, a glossiness measuring device 198 for measuring the glossiness of the peripheral surface 32b of the casting drum is installed on the downstream side in the drum running direction with respect to the drum washer 150.

  The first nozzle 151 includes a carrier gas inlet 162 into which the carrier gas 300 is introduced, a carbon dioxide inlet 163 into which the liquid carbon dioxide 310 is introduced, a cleaning gas blowing port 164 that sends out the cleaning gas 320, and a carrier gas. A carrier gas channel 165 that communicates the inlet 162 and the cleaning gas blower 164 and a carbon dioxide channel 166 that communicates the carbon dioxide inlet 163 and the carrier gas channel 165 are provided. The carrier gas channel 165 includes a cleaning gas forming unit 167 that generates a cleaning gas 320 including dry ice particles 311 from the liquid carbon dioxide 310 from the carrier gas 300 and the carbon dioxide channel 166. Further, the carbon dioxide channel 166 has an orifice 168 on the outlet 166a side. Further, the carrier gas flow path 165 has a rectifying pocket 169 having a cross-sectional area larger than the cross-sectional area of the carrier gas flow path 165 on the upstream side of the cleaning gas forming portion 167.

  The second nozzle 152 includes a cleaning gas introduction port 175 into which the cleaning gas 320 from the cleaning gas blowing port 164 is introduced, a cleaning gas supply port 176 that sends out the cleaning gas 320, a carrier gas introduction port 175, and a cleaning gas blowing port 176. And a cleaning gas flow path 177 for communicating with each other. The cleaning gas channel 177 has a rectifying pocket 178 having a cross-sectional area larger than that of the cleaning gas channel 177.

  The second nozzle 152 is attached to the first nozzle 151 such that the cleaning gas blowing port 164 and the cleaning gas introduction port 175 are connected. The drum washer 150 is arranged so that the distance L1 between the peripheral surface 32b of the casting drum 32 and the cleaning gas blower port 176 and the spray angle θ1 become desired values. In addition, since the installation conditions (L1, θ1, etc.) of the drum washer for the vicinity of the casting drum may be the same as described above, description thereof is omitted here.

  The carrier gas inlet 162 is connected via a pipe 180 to a carrier gas tank 181 that is a supply source of the carrier gas 300. The carrier gas tank 181 is provided with a pressure regulator 191a for adjusting the pressure inside the tank. The pipe 180 is provided with a throttle valve 182 that adjusts the flow rate of the carrier gas 300. The carbon dioxide inlet 163 is connected to a carbon dioxide tank 191 that is a supply source of the liquid carbon dioxide 310 via the pipe 190. The pipe 190 is provided with a throttle valve 192 that adjusts the flow rate of the liquid carbon dioxide 310. The pipe 180 is provided with a flow meter 200, and the pipe 190 is provided with a temperature controller 201, a flow meter 202, a pressure sensor 203, and a temperature sensor 204.

  As the carrier gas 300, for example, air is used. The carrier gas tank 181 may store the carrier gas 300 in a state compressed to a predetermined pressure. As the liquid carbon dioxide 310, it is preferable to use one having high purity. In addition, as conditions for the carbon dioxide tank 191 and the pipe 190, the liquid carbon dioxide 310 sent from the carbon dioxide tank 191 can be maintained in a liquid state before reaching the cleaning gas forming unit 167. Good.

  The throttle valves 182 and 192 are controlled by the controller 195. The controller 195 includes a memory 195a. The memory 195a supplies the liquid carbon dioxide 310 and the carrier gas tank 181 when the cleaning performance for the peripheral surface 32b of the casting drum is the highest (hereinafter referred to as “optimum supply amount”). And the pressure in the pipe 190 when the cleaning performance is highest (hereinafter referred to as “optimum pressure”) and the temperature of the liquid carbon dioxide 310 when the cleaning performance is highest (hereinafter referred to as “optimum temperature”). Is remembered. Further, the memory 195a stores the glossiness of the peripheral surface 32b of the casting drum and the cleaning time required for achieving the glossiness in association with each other. Here, the glossiness of the peripheral surface 32b is used as an index indicating the cleanability of the peripheral surface 32b. In addition, by adjusting the opening degree of the throttle valves 182 and 192, the spraying pressure of the cleaning gas 320, the particle size of the dry ice particles 311, the mixing ratio of the carrier gas 300 and the liquid carbon dioxide 310 may be adjusted. Is possible.

  The controller 195 adjusts the opening amounts of the throttle valves 182 and 192 based on the flow rates of the liquid carbon dioxide 310 and the carrier gas tank 181 measured by the flow meters 200 and 202, and controls the supply amounts of the liquid carbon dioxide 310 and the carrier gas 300. It approaches the optimum supply amount (hereinafter referred to as “CO2 and carrier gas supply amount feedback control”). By performing feedback control of the CO 2 and carrier gas supply amount, the problem of dry ice clogging in the first and second nozzles 151 and 152 of the drum washer 150 can be solved. Thereby, it is possible to perform cleaning with a constant capacity without degrading the cleaning performance.

  FIG. 4A shows the change over time of the flow rate of liquid carbon dioxide 310 (hereinafter referred to as “CO 2 flow rate”) during drum cleaning. Here, “◯” in FIG. 4A indicates the CO2 flow rate when the feedback control of the CO2 and carrier gas supply amounts is performed, and “□” indicates the case where the feedback control of the CO2 and carrier gas supply amounts is not performed. As for the CO2 flow rate, the hatching area 210 shows the CO2 flow rate when the cleaning performance for the peripheral surface 32b of the casting drum is not good. As shown in FIG. 4A, when the feedback control of the CO2 and the carrier gas supply amount is performed, the CO2 flow rate is kept constant even if the cleaning time becomes long, so that cleaning is performed with a constant capacity. be able to.

  The controller 195 controls the pressure regulator 191 a based on the pressure in the pipe 190 measured by the pressure sensor 203 to adjust the supply pressure of the carbon dioxide tank 191. By adjusting the supply pressure of the carbon dioxide tank 191, the pressure in the pipe 190 is brought close to the optimum pressure (hereinafter referred to as “CO2 pipe pressure feedback control”). By performing feedback control of the CO2 piping internal pressure, a decrease in the cylinder internal pressure due to the low temperature of the carbon dioxide tank 191 can be suppressed. Thereby, since the supply pressure of the liquid carbon dioxide 310 is maintained constant, cleaning can be performed with a constant capacity.

  FIG. 4B shows a change with time of the pressure in the pipe 190 (hereinafter referred to as “CO2 pipe internal pressure”) during drum cleaning. Here, “◯” in FIG. 4B indicates the pressure in the CO2 pipe when the feedback control of the pressure in the CO2 pipe is performed, and “□” indicates the inside of the CO2 pipe when the feedback control of the pressure in the CO2 pipe is not performed. The hatching area 211 indicates the pressure in the CO 2 pipe when the cleaning performance for the peripheral surface 32b of the casting drum is not good. As shown in FIG. 4B, by performing feedback control of the CO2 pipe internal pressure, the cleaning performance can be maintained even if the cleaning time is increased.

  The controller 195 controls the temperature regulator 201 based on the temperature of the liquid carbon dioxide 310 measured by the temperature sensor 204 to bring the temperature of the liquid carbon dioxide 310 close to the optimum temperature (hereinafter referred to as “CO2 temperature feedback control”). . For example, when the temperature in the pipe 190 is warmed in summer or when there is a change in cooling capacity, the temperature of liquid carbon dioxide rises, which may make cleaning difficult. On the other hand, the temperature of liquid carbon dioxide is kept constant by performing feedback control of the CO2 temperature. Thereby, it is possible to perform cleaning with a constant capacity. The optimum temperature of the liquid carbon dioxide 310 is preferably a temperature at which the ratio of becoming a gas becomes the highest, for example, −5 ° C. Further, the feedback control of the CO2 temperature is also effective when the drum cleaner 150 is continuously operated, for example, continuously operated for 10 minutes or more.

  FIG. 4C shows a change with time of the temperature of the liquid carbon dioxide 310 (hereinafter referred to as “CO2 temperature”) during drum cleaning. Here, “◯” in FIG. 4C indicates the CO2 temperature when the CO2 temperature is brought close to the optimum temperature based on the detection result of the temperature sensor 204 (hereinafter referred to as “CO2 temperature feedback control”), and “□” The hatched area 222 indicates the CO2 temperature when the cleaning performance for the peripheral surface 32b of the casting drum is not good when the feedback control of the CO2 temperature is not performed. As shown in FIG. 4C, by performing the feedback control of the CO2 temperature, the cleaning performance can be maintained even if the cleaning time becomes long.

The controller 195 measures the cleaning time required to obtain the glossiness based on the glossiness of the peripheral surface 32b of the casting drum measured by the glossiness measuring device 198. When the measured cleaning time exceeds the cleaning time stored in the memory 195 a, the controller 195 increases the opening of the throttle valves 182 and 192 and supplies the carrier gas 181 and the liquid carbon dioxide 310. Increase. Thereby, the spraying amount of the cleaning gas 320 is increased and the cleaning ability is improved. Note that the supply amount of the liquid carbon dioxide 310 is preferably 120 kg / h / mm ² in a normal state and 150 kg / h / mm ² in a case where the cleaning capability is improved. In addition, the supply amount of the carrier gas 300 is preferably 5 m ³ / min / mm ² at normal times and 6.5 m ³ / min / mm ² at the time of improvement in cleaning capability.

  FIG. 5 shows the change over time of the glossiness (hereinafter simply referred to as “glossiness”) of the peripheral surface 32b of the casting drum during drum cleaning. As for the “glossiness” in FIG. 5, “1” has the highest glossiness, the glossiness decreases as “1” increases, and “4.5” has the lowest glossiness. “◯” in FIG. 5 indicates the glossiness when the cleaning performance is not increased, “Δ” indicates the glossiness when the cleaning capability is increased, and “□” indicates the glossiness stored in the memory 195a of the controller. ing. In FIG. 5, it takes a lot of cleaning time to change the glossiness of the peripheral surface 32b from “3.5” to “3”. However, the excess of this cleaning time is detected by the controller 195, and the cleaning capability is accordingly detected. By raising the value, it is possible to prevent unexpected time extension.

Next, the operation of the drum washer 150 will be described. Under the control of the controller 195, the opening degree of the throttle valves 182 and 192 is adjusted to a desired range, respectively. The carrier gas 300 is introduced from the carrier gas tank 181 to the carrier gas inlet 162 via the pipe 180 at a predetermined flow rate Q1 (m ³ / mm · min) and sent to the cleaning gas forming unit 167 of the carrier gas channel 165. It is done. The liquid carbon dioxide 310 is introduced from the carbon dioxide tank 191 to the carbon dioxide inlet 163 through the pipe 190 at a predetermined mass flow rate Q2 (kg / mm · min), and sent to the carbon dioxide channel 166. The liquid carbon dioxide 310 sent to the carbon dioxide channel 166 is sent to the cleaning gas forming unit 167 via the orifice 168. The liquid carbon dioxide 310 sent to the cleaning gas forming unit 167 becomes carbon dioxide gas and dry ice particles 311 due to phase change. Then, due to the flow of the carrier gas 300, the carbon dioxide gas and the dry ice particles 311 collide with the organic matter X1 deposited on the peripheral surface 32b. The organic substance X1 is removed from the peripheral surface 32b by the collision between the dry ice particles 311 and the organic substance X1.

  In the drum washer 150, feedback control of the CO2 and carrier gas supply amount, feedback control of the CO2 pipe internal pressure, and feedback control of the CO2 temperature are performed, and the cleaning ability for the peripheral surface 32b of the casting drum is kept constant. In addition, the cleaning time required to make the glossiness of the peripheral surface 32b a predetermined glossiness is measured, and when the cleaning time exceeds a preset cleaning time, the cleaning capability is increased, thereby extending an unexpected time. prevent.

  The removal action of the organic substance X1 includes (1) the kinetic energy of the dry ice particles sprayed by the collision between the dry ice particles and the organic substance X1 is used to destroy the organic substance X1 adhering to the peripheral surface 32b, and (2) the organic substance Dry ice particles become liquid carbon dioxide due to collision with X1, and the liquid carbon dioxide dissolves the organic substance X1, and (3) volume expansion due to vaporization of liquid carbon dioxide and dry ice particles is an organic substance. The synergistic effect by blowing off X1 and the combination of (1)-(3) is mentioned. Due to the effect caused by the collision with the dry ice particles, the organic substance X1 removed from the peripheral surface 32b is miniaturized and circulated together with the atmospheric gas. Will not lead to. Moreover, even if it remains on the peripheral surface 32b, it is a minute object and does not develop into a precipitate failure due to this.

  In the second embodiment, the flow rate of the liquid carbon dioxide 310 is measured for the liquid carbon dioxide 310, and feedback control is performed based on the measurement result. However, the solid carbon dioxide, that is, the dry ice particles 311 Even in this case, the same feedback control can be performed.

  In the second embodiment, the drum cleaner 150 including the first nozzle 151 and the second nozzle 152 is used. However, the present invention is not limited to this, and only the first nozzle 151 may be used as the drum cleaner. Although not shown, it is preferable to provide a suction duct in the vicinity of the drum washer 150 to suck and collect the pulverized organic matter.

  Further, the use of ultraviolet rays, oxygen radicals, and lasers is also effective for removing organic substances adhering to the surface of the casting drum 32. Next, an example of a method for cleaning a support using ultraviolet rays according to the third embodiment of the present invention will be described. In the following description, only portions different from the first embodiment will be described, and other descriptions will be omitted.

  As shown in FIG. 6, the ultraviolet lamp 500 that is the drum cleaner 242 is a low-pressure mercury lamp having a strong line spectrum at two wavelengths of 185 nm and 254 nm. If necessary, the ultraviolet lamp 500 irradiates the surface of the casting drum 32 with ultraviolet rays. Note that the ultraviolet lamp is not limited to the above, and an excimer lamp, a high-pressure mercury lamp, a metal halide lamp, or the like that enables ultraviolet irradiation with a wavelength of 172 nm is preferably used.

  A built-in controller is connected to the ultraviolet lamp 500. The built-in controller is provided with a timer function, and ON / OFF related to irradiation of the ultraviolet lamp 500 is controlled based on a predetermined irradiation time. When irradiating ultraviolet rays, the built-in controller turns on the ultraviolet lamp 500 and irradiates the casting drum 32 with ultraviolet rays from the ultraviolet lamp 500 based on a predetermined irradiation time. The ultraviolet lamp 500, which is a low-pressure mercury lamp, is characterized by strong line spectra of 185 nm and 254 nm. The energy of the ultraviolet rays of the respective wavelengths is 155 (kcal / mol) when the wavelength is 185 nm, and the wavelength is 254 nm. In this case, it is 113 (kcal / mol). On the other hand, the single bond energies of C—C, C—H, C═C, OH, and C—O, which are the main bonds constituting the organic matter described above, are 84.3 (kcal / mol) and 97. 6 (kcal / mol), 140.5 (kcal / mol), 110.6 (kcal / mol) and 74.6 (kcal / mol). For this reason, among the bonds of organic substances such as fatty acid esters by the ultraviolet rays irradiated on the surface of the casting drum 32, the bonds with a binding energy lower than the energy of the ultraviolet rays are broken, and the organic substances attached to the surface of the casting drum 32. Is disassembled.

At this time, ultraviolet molecules having a wavelength of 185 nm are absorbed by oxygen molecules in the casting chamber 12 to produce ozone molecules. In addition, ultraviolet rays having a wavelength of 254 nm are absorbed by ozone molecules, and excited oxygen atoms O ( ¹ D) are produced. Furthermore, ground state oxygen atoms O ( ³ P) are produced from ozone molecules by thermal decomposition. The oxygen atoms O ( ¹ D) and oxygen atoms O ( ³ P) having such a strong oxidizing power and the fatty acid esters adhering to the surface of the casting drum 32 due to ultraviolet rays are decomposed to produce CO ₂ , CO, and H _2. Zero and low molecular weight compounds are produced. In order to absorb and recover CO ₂ , CO, and H ₂ O generated by these decomposition reactions, it is preferable to install an adsorption duct (not shown) in the vicinity of the ultraviolet lamp 500. The product is recovered by the condenser 39 in the casting chamber 12, and the low molecular compound is dissolved in the dope 21 to form a new casting film 33 on the surface of the casting drum 32. Therefore, there is no problem in film quality. When a predetermined irradiation time has elapsed, the ultraviolet lamp 500 is turned off by the built-in controller, and the ultraviolet radiation of the ultraviolet lamp 500 is stopped.

  The oxygen molecules that can generate ozone molecules by irradiation with ultraviolet rays having a wavelength of 185 nm may be either those in the casting chamber where the casting process is performed or those supplied from the outside of the casting chamber. In the above embodiment, ultraviolet rays having a wavelength of 185 nm or 254 nm are applied to remove the organic substances adhering to the surface of the casting drum 32. However, the present invention is not limited to this, and the binding of organic substances including fatty acid esters is broken. If possible, the same effect can be obtained by irradiating ultraviolet rays with other wavelengths (for example, wavelength 172 nm).

  The effect of removing organic substances by the irradiation of ultraviolet rays depends on the distance L2 between the surface of the casting drum 32 and the ultraviolet lamp 500, the irradiation time, and the surface temperature of the casting drum 32. In the present invention, the distance L2 between the ultraviolet lamp 500 and the surface of the casting drum 32 is preferably 25 mm or more and 50 mm or less, more preferably 25 mm or more and 30 mm or less. If L3 is less than 25 mm, the surface temperature of the casting drum 32 increases due to the irradiation of the ultraviolet lamp 500, and the peelability of the casting film 33 cannot be maintained. On the other hand, when the distance L2 exceeds 50 mm, organic substances such as fatty acid esters are not sufficiently decomposed.

  The irradiation time of ultraviolet rays in the present invention is preferably 60 minutes or more and 180 minutes or less, and more preferably 120 minutes or more and 180 minutes or less. If the irradiation time is 120 minutes, a removal effect is seen on the entire surface of the casting drum 32, and if the irradiation time is 180 minutes, the removal effect is sufficiently exhibited. However, if the irradiation time for irradiating the surface of the casting drum 32 with ultraviolet rays is less than 60 minutes, it is difficult to sufficiently decompose the organic matter. In addition, when irradiation time is 180 minutes as mentioned above, since the decomposition effect of the organic substance satisfactory is acquired, it is not necessary to extend any more.

  Next, an example of a method for cleaning the surface of the support using oxygen radicals will be described. In the following description, only portions different from the first embodiment will be described, and other descriptions will be omitted. As shown in FIG. 7, the drum washer 142 used in the fourth embodiment includes a nozzle 400 attached to the tip of a pipe 403, a cover 402 that covers the outer periphery of the nozzle 400, and the like. A supply port 400 a that opens to the casting drum 32 is formed at the tip of the nozzle 400. The cover 402 preferably has a suction function capable of sucking the vicinity of the supply port 400a. The nozzle 400 is connected to a shift unit that can freely adjust the position of the nozzle 400, and the distance L3 between the supply port 400a and the casting drum 32 is suitably adjusted. A plasma generator 405 is connected to the pipe 403.

  The plasma generator 405 is provided with a gas filling chamber and a timer (not shown). The gas filling chamber is filled with a predetermined gas containing oxygen and stores an electrode pair therein. The timer is for generating and supplying oxygen radicals for a predetermined time. In the gas filling chamber, a predetermined voltage is applied between the electrodes to generate oxygen radicals from oxygen molecules contained in the filled gas. The generated oxygen radicals are sent to the drum cleaning machine 142 via the pipe 403.

During the supply time determined by the operation of the timer, oxygen radicals are sent from the plasma generator 405 into the pipe 403, and oxygen radicals are further supplied from the supply port 400 a to the surface of the casting drum 32. The oxygen radicals react with organic substances attached to the surface of the casting drum 32. Organic substances mainly composed of fatty acid esters or the like are decomposed into CO ₂ , CO, H ₂ O, low molecular compounds, and the like and efficiently removed. In addition to fatty acid esters, oxygen radicals also efficiently decompose organic substances such as fatty acids and metal fatty acid salts. The substance generated by the oxygen radicals is recovered by the cover 402 having a suction function and the condenser 39 together with the organic solvent gas present in the casting chamber 12. Further, since the low molecular weight compound dissolves in the dope 21 cast on the surface of the casting drum 32 and becomes a new casting film 33, there is no problem in the quality of the film. The oxygen molecules that generate oxygen radicals may be either floating in the casting chamber or supplied from outside the casting chamber.

  The organic substance decomposition effect due to the supply of oxygen radicals includes the supply distance L3 between the surface of the casting drum 32 and the supply port 400a of the nozzle 400, the angle θ2 formed by the oxygen plasma supply direction and the surface of the casting drum 32, and the supply. Depends on time etc. In the present invention, the distance L3 is preferably 2 mm or more and 15 mm or less, more preferably 2 mm or more and 5 mm or less. Here, when L3 is less than 2 mm, the casting drum 32 may be damaged by bringing the nozzle 400 close to the casting drum 32. Further, when the nozzle 400 having a high temperature (250 ° C. to 350 ° C.) is brought close to the casting drum 32, the temperature of the casting drum 32 rises, resulting in deterioration of the drum surface due to thermal history and temperature difference on the drum. There is concern about changes in film thickness. On the other hand, when the distance L3 is greater than 15 mm, the oxygen radicals are not sufficiently supplied to the surface of the casting drum 32, so that the effect of decomposing the fatty acid ester by the oxygen radicals is not sufficiently exhibited.

  The angle θ2 formed by the direction in which the oxygen plasma is supplied and the surface of the casting drum 32 is preferably 30 ° or more and 150 ° or less, more preferably 45 ° or more and 135 ° or less, and most preferably 85 ° or more and 95 °. It is as follows. In particular, oxygen radicals can be supplied to the surface of the casting drum 32 as the angle θ2 is made closer to a right angle. The supply time for supplying oxygen radicals to the surface of the casting drum 32 is preferably 0.025 seconds or more and 0.05 seconds or less, more preferably 0.375 seconds or more and 0.05 seconds or less. When the supply time is 0.025 seconds, the fatty acid ester decomposition effect on the casting drum 32 is partially observed. On the other hand, a supply time of 0.05 seconds is sufficient to decompose all the fatty acid esters on the surface of the casting drum 32.

  In the above-described embodiment, the form in which oxygen radicals are generated by the plasma generator 405 installed outside the casting chamber 12 is shown. However, the present invention is not limited thereto, and oxygen molecules floating in the casting chamber 12 are used. Even if oxygen radicals are generated and supplied to the surface of the casting drum 32, the same effect can be obtained.

  In the present invention, since it is not necessary to stop the production equipment or reduce the production speed at the time of washing, it is possible to produce a high-quality film without reducing the productivity. Further, if the non-contact type drum washer described in each of the above embodiments is used, organic substances can be removed without generating cleaning marks or scratches on the surface of the casting drum. The drum cleaning machine applicable to the present invention is not limited to the above embodiment, and examples thereof include an apparatus that enables laser irradiation. In the present invention, a drum cleaner equipped with a nonwoven fabric or the like may be used. However, when a wiping device is used, it is preferably used in combination with the non-contact type drum cleaner described in each embodiment. In addition to the above, in the above-described embodiment, a so-called online mode is described in which organic substances on the surface of the casting drum are removed in the film manufacturing facility, but the same removal treatment is performed on the surface of the casting drum taken out from the film manufacturing facility. Organic substances may be removed in an off-line form.

  Hereinafter, the dope according to the present invention will be described.

In the present embodiment, cellulose acylate is used as the polymer, and cellulose triacetate (TAC) is particularly preferable as the cellulose acylate. Among cellulose acylates, those in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is 3 carbon atoms. The substitution degree of the acyl group of ˜22. In addition, it is preferable that 90 mass% or more of TAC is a particle | grain of 0.1-4 mm. However, the polymer that can be used in the present invention is not limited to cellulose acylate.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl groups of cellulose are esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  The total degree of acylation substitution, that is, the value of DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the acyl substitution degree at the 2-position), and DS3 is the hydroxyl group at the 3-position in the glucose unit. This is the rate at which hydrogen is substituted by an acyl group (hereinafter referred to as the 3-position acyl substitution degree), and DS6 is the rate at which the hydrogen at the 6-position hydroxyl group is substituted by an acyl group in a glucose unit (hereinafter, (Referred to as the degree of acyl substitution at the 6-position).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. These cellulose acylates By using, a solution (dope) having better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

  Cellulose, which is a raw material of cellulose acylate, may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton.

  The acyl group having 2 or more carbon atoms of the cellulose acylate in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. For example, cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like may be mentioned, and each may further have a substituted group. Preferred examples of these include propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group. , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. It is.

  Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-butanol, Diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among the above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms are preferable, and dichloromethane is most preferable. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength and optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are mixed in addition to dichloromethane. It is preferable to do. As for content of alcohol, 2-25 mass% is preferable with respect to the whole solvent, More preferably, it is 5-20 mass%. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, and n-butanol, but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition that does not use dichloromethane has been studied for the purpose of minimizing the impact on the environment. In this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferable. Sometimes used. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester and alcohol (that is, —O—, —CO—, —COO— and —OH) can also be used as the solvent.

  Details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and release accelerators. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516], and these descriptions can also be applied to the present invention.

  In the solution casting method of the present invention, when casting a dope, two or more types of dopes are simultaneously co-cast and laminated, or a plurality of dopes are sequentially co-cast. Sequential lamination co-casting can be performed. In addition, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. However, it is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5 to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. . In addition, when performing simultaneous lamination and co-casting, it is preferable that the high-viscosity dope is enveloped by the low-viscosity dope when the dope is cast from the die slit to the support, and is formed from the die slit to the support. Of the casting beads, the dope in contact with the outside world preferably has a higher alcohol composition ratio than the inner dope.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each step, handling method, curling, winding method after flatness correction, solvent recovery method, film recovery method Until now, the details are described in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  Examples of the present invention will be described below to explain the effects of the present invention. In addition, the Example and comparative example shown here are examples which concern on this invention, and do not limit this invention.

  In Example 1, first, in the film manufacturing facility 10, the surface is subjected to chrome plating and mirror finishing, and the dope 21 is cast on the surface of a cylindrical casting drum 32 having a diameter of 1000 mm with a dry thickness of 80 μm. Thus, a casting film 33 was formed. While the casting film 33 having self-supporting property was supported by the peeling roller 36, the wet film 38 was peeled off. The wet film 38 was dried to a predetermined residual solvent amount by the transfer part 13 and the tenter 14 to obtain a film 20. Thereafter, the film 20 is sent to the drying chamber 15 and dried until the amount of solvent remaining in the film 20 is desired, and then the cooling chamber 16 is brought to a substantially room temperature and is wound in the winding chamber 17. A roll 51 was obtained with the roller 51.

  During film formation, the cleaning gas was constantly blown onto the surface of the casting drum 32 until the dope was cast after the casting film 33 was peeled off by the drum washer 41. The drum washer 41 was a snocle manufactured by Linkstar Japan, and the nozzle 65 was a nozzle with an orifice made of Teflon (registered trademark). The cleaning gas used was air containing dry ice particles having an average particle size of 15 μm. At this time, the surface temperature of the casting drum 32 was −10 ° C. Further, the distance L1 from the blower opening 65a of the nozzle 65 to the surface of the casting drum 32 is 15 mm, the blowing pressure is 896 kPa, and the angle θ1 between the surface of the casting drum 32 and the gas blowing direction is 90 °. did.

  Using the completed film 20 as a sample, the presence or absence of optical unevenness was examined with a haze meter. As a result, no optical unevenness was observed on the film. Further, it was confirmed whether or not there was damage on the surface of the casting drum 32 after the gas was sprayed by an optical microscope, but neither the presence of organic substances nor the damage due to the spraying of the cleaning gas was confirmed.

  In Example 2, the film 20 was manufactured in the same manner as in Example 1 except that the cleaning gas was intermittently blown. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  In Example 3, a film 20 was produced in the same manner as in Example 1 except that an ultraviolet lamp was used as a drum washer and that the surface of the casting drum 32 was always irradiated with ultraviolet rays. As the ultraviolet lamp, SLC-500ATK (low pressure mercury) manufactured by GS Yuasa Lighting Co., Ltd. was used. The distance L2 between the ultraviolet lamp and the casting drum 32 was 20 mm. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  In Example 4, a film 20 was produced in the same manner as in Example 3 except that ultraviolet rays were irradiated intermittently. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  In Example 5, a film 20 was manufactured in the same manner as in Example 1 except that a plasma generator was used as a drum washer and oxygen plasma was constantly irradiated onto the surface of the casting drum 32. As the plasma generator, Aiplasma (registered trademark) manufactured by Matsushita Electric Works Co., Ltd. was used. The distance L3 from the oxygen plasma supply port to the surface of the casting drum 32 was 7 mm. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  In Example 6, a film 20 was manufactured in the same manner as Example 5 except that oxygen plasma was intermittently irradiated. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  In Example 7, SAMAC, CL500Q was used as a drum washer, and the removal of organic substances was attempted by always irradiating the surface of the casting drum 32 with a laser. Film 20 was produced. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

  Example 8 is the same as Example 7 except that SAMAC, CL500Q was used as a drum washer, and the surface of the casting drum 32 was intermittently irradiated with a laser to try to remove organic matter. Thus, a film 20 was produced. As a result, no optical unevenness was confirmed in the completed film 20. Moreover, although presence or the presence or absence of the organic substance in the surface of the casting drum 32 was confirmed similarly to Example 1, neither was confirmed.

[Comparative Example 1]
In Comparative Example 1, a film was produced under the same conditions as in Example 1 without using a non-contact type drum washer. Further, after a predetermined time had elapsed from the start of film formation, the surface of the casting drum 32 was washed with a nonwoven fabric soaked with acetone as a solvent before the dope was cast after the casting film 33 was peeled off. As a result, optical unevenness was confirmed in the completed film 20. Further, it was possible to visually confirm the adhesion of organic substances on the surface of the casting drum 32 at an early stage from the start of film formation.

It is the schematic of an example of the film manufacturing equipment concerning this invention. It is the schematic of an example which wash | cleans the surface of a casting drum using the drum washing machine which is 1st Embodiment. It is the schematic of an example which wash | cleans the surface of a casting drum using the drum washing machine which is 2nd Embodiment. (A) is a graph showing changes in the flow rate of liquid carbon dioxide during drum cleaning, (B) is a graph showing changes in the pressure of liquid carbon dioxide during drum cleaning, and (C) is drum cleaning. It is a graph which shows the change of the temperature of the liquid carbon dioxide in time. It is a graph which shows the change of the glossiness of the surrounding surface of a casting drum at the time of drum washing | cleaning. It is the schematic of an example which wash | cleans the surface of a casting drum using the drum washing machine which is 3rd Embodiment. It is the schematic of an example which wash | cleans the surface of a casting drum using the drum washing machine which is 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film production equipment 12 Casting chamber 20 Film 21 Dope 30 Casting die 32 Casting drum 32b Circumferential surface 33 (Casting drum) Casting film 34 Decompression chamber 36 Stripping rollers 41, 142, 150, 242, Drum cleaning Machine 167 Cleaning gas generation unit 180, 190 Piping 181 Carrier gas tank 182, 192 Throttle valve 191 Carbon dioxide tank 191a Pressure regulator 195 Controller 195a Memory 198 Glossiness measuring instrument 200, 202 Flow meter 201 Temperature regulator 203 Pressure sensor 204 Temperature sensor 300 Carrier gas 310 Liquid carbon dioxide

Claims (11)

A step of casting a dope containing a polymer and a solvent on the surface of a support that runs endlessly to form a cast film;
Peeling the casting film from the support and drying to form a film;
A cleaning step of cleaning the surface of the support until the dope is cast after the casting film is peeled off, and suppressing an increase in organic matter adhering to the surface;
A solution casting method characterized by comprising:   2. The solution casting method according to claim 1, wherein in the cleaning step, a cleaning gas containing granular dry ice is sprayed constantly or intermittently on the surface of the support by a cleaning gas spraying means. In the washing step,
A dry ice supply unit for supplying the dry ice; a carrier gas supply unit for supplying a carrier gas for transporting the dry ice to the surface of the support; and the cleaning gas by mixing the dry ice with the carrier gas. Spraying the cleaning gas onto the surface of the support by the cleaning gas spraying means having a cleaning gas generating unit to generate,
The flow rate of the dry ice is measured by a first flow rate measuring unit provided in a first pipe connecting the dry ice supply unit and the cleaning gas generation unit, and the carrier gas supply unit and the cleaning gas generation unit are connected to each other. The flow rate of the carrier gas is measured by a second flow rate measuring unit provided in the second pipe,
The supply amount of the dry ice and the supply amount of the carrier gas are feedback-controlled based on the flow rate of the dry ice and the flow rate of the carrier gas measured by the first and second flow rate measuring units. Item 3. The solution casting method according to Item 1 or 2. In the washing step,
Measure the pressure in the first pipe by the pressure measuring unit provided in the first pipe,
The solution casting method according to claim 3, wherein the supply pressure of the dry ice is feedback-controlled based on the pressure in the first pipe measured by the pressure measuring unit. In the washing step,
The temperature of the dry ice is measured by a temperature measuring unit provided in the first pipe,
5. The solution casting method according to claim 3, wherein the temperature of the dry ice is feedback-controlled based on the temperature of the dry ice measured by the temperature measuring unit. In the washing step,
The gloss measurement unit provided on the downstream side in the running direction of the support with respect to the cleaning gas spraying means measures the gloss of the surface of the support and makes the surface of the support a predetermined gloss. The time required for cleaning is measured by the time measurement unit,
6. The spray amount of the cleaning gas is controlled based on the glossiness of the surface of the support measured by the glossiness measurement unit and the cleaning time measured by the time measurement unit. The solution casting method according to claim 1.   7. The solution casting method according to claim 1, wherein in the cleaning step, the surface of the support is irradiated with ultraviolet rays constantly or intermittently.   The solution casting method according to claim 1, wherein in the cleaning step, the surface of the support is irradiated with plasma constantly or intermittently.   9. The solution casting method according to claim 1, wherein in the cleaning step, the surface of the support is irradiated with a laser constantly or intermittently.   10. The surface of the support is cooled to −10 ° C. or more and 10 ° C. or less, and the cast film is gelled to have self-supporting property. Solution casting method. The polymer is cellulose triacetate;
11. The solution casting method according to claim 1, wherein the organic substance includes any one of a fatty acid, a fatty acid ester, and a fatty acid metal salt.

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